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A289986 Number of connected 2n-regular loopless multigraphs on 2n unlabeled nodes. 4
1, 1, 3, 120, 543116, 635669057538, 112368754788708539549 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,3
COMMENTS
Multigraphs are loopless.
There are no (2n+1)-regular multigraphs with (2n+1) number of points, for every nonnegative n.
LINKS
FORMULA
a(n) = A328682(2*n, 2*n). - Andrew Howroyd, Mar 18 2020
PROG
(nauty/bash) for n in {1..4}; do geng -c -d1 $[2*$n] -q | multig -m$[2*$n] -r$[2*$n] -u; done
CROSSREFS
Sequence in context: A289704 A246292 A202768 * A301559 A141440 A156001
KEYWORD
nonn,more,hard
AUTHOR
Natan Arie Consigli, Aug 19 2017
EXTENSIONS
a(5)-a(6) from Andrew Howroyd, Mar 18 2020
STATUS
approved

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Last modified February 21 13:52 EST 2024. Contains 370235 sequences. (Running on oeis4.)